1. Field of the Invention
The present invention relates to a process for hydrogenating organic compounds which have at least one carbonyl group using a catalyst which is distinguished inter alia in that it consists of copper oxide, aluminum oxide and at least one of the oxides of lanthanum, tungsten, molybdenum, titanium or zirconium and in that a catalyst with high selectivity and, at the same time, high stability is produced through the addition of oxides of lanthanum, tungsten, molybdenum, titanium or zirconium. In the preparation thereof it is possible additionally to add copper powder, copper flakes or cement. The present invention likewise relates to the catalyst per se and very generally to the use of lanthanum oxide in the preparation of catalysts with high selectivity and, at the same time, high stability.
2. Description of the Background
The catalytic hydrogenation of carbonyl compounds such as, for example, carboxylic acids or carboxylic esters occupies an important position in the production sequences in the basic chemicals industry.
The catalytic hydrogenation of carbonyl compounds such as, for example, carboxylic esters is carried out in industrial processes almost exclusively in fixed bed reactors. The fixed bed catalysts used are, besides catalysts of the Raney type, especially supported catalysts, for example copper, nickel or noble metal catalysts.
U.S. Pat. No. 3,923,694 describes, for example, a catalyst of the copper oxide/zinc oxide/aluminum oxide type. The disadvantage of this catalyst is that it has insufficient mechanical stability during the reaction and therefore disintegrates relatively quickly. This results in a loss of activity and a build up of a difference in pressure across the reactor owing to the disintegrating catalyst shaped articles. It is consequently necessary to shut down the plant prematurely.
DE 198 09 418.3 describes a process for the catalytic hydrogenation of a carbonyl compound in the presence of a catalyst which comprises a support, which mainly contains titanium dioxide, and as active component copper or a mixture of copper with at least one of the metals selected from the group of zinc, aluminum, cerium, a noble metal and a group VIII metal, where the copper surface area does not exceed 10 m2/g. Preferred support materials are mixtures of titanium dioxide with aluminum oxide or zirconium oxide or aluminum oxide and zirconium oxide. In a preferred embodiment, the catalyst material is shaped with addition of metallic copper powder or copper flakes.
DE-A 195 05 347 describes very generally a process for preparing catalyst tablets of high mechanical strength, where a metal powder or a powder of a metal alloy is added to the material to be tableted. The metal powder added is, inter alia, aluminum powder or copper powder or copper flakes. However, on addition of aluminum powder in the case of a copper oxide/zinc oxide/aluminum oxide catalyst, the resulting shaped article has a side crushing strength which is worse than that of a shaped article prepared without addition of aluminum powder, and the shaped article of the invention showed, when used as catalyst, a conversion activity which was less than that of catalysts prepared without addition of aluminum powder. Likewise disclosed therein is a hydrogenation catalyst composed of NiO, ZrO2, MoO3 and CuO, to which Cu powder inter alia was admixed during the preparation. However, no statements are made in this publication about the selectivity or the activity.
DE 256 515 describes a process for preparing alcohols from synthesis gas, employing catalysts based on Cu/Al/Zn which are obtained by grinding and pelletizing together with metallic copper powder or copper flakes. The main object of the described process is to prepare mixtures of C1 to C5 alcohols, the process being managed in such a way that the upper third of the layer in the reactor contains a catalyst which has a higher content of copper powder or copper flakes, and the lower third contains a catalyst which has a lower content of copper powder or copper flakes.